This invention relates to a speed sensor assembly for an automotive adaptive braking system.
Existing vehicle speed sensors include a tone wheel of a relatively large diameter and an electromagnetic pickup device which must be mounted on a non-rotative portion of the vehicle adjacent the tone wheel, which, of course, is mounted for rotation with the corresponding vehicle wheel. The spacing between the sensor pickup and the tone wheel is extremely critical, and has customarily been set when the vehicle is assembled. Of course, since the tone wheel rotates with the vehicle wheel, which may deflect relative to the sensor, this distance may vary during the life of the vehicle. Furthermore, since both the tone wheel and the sensor pickup are exposed on the underside of the vehicle, the rather adverse environment in which they must operate sometimes causes problems.
The present invention relates to a speed sensor which uses a small diameter tone wheel and an electromagnetic pickup device which are mounted in a housing with all critical dimensions established at the time of manufacture of the speed sensor and not at the time that the speed sensor is installed on the vehicle. Furthermore, the entire package consisting of the tone wheel and electromagnetic pickup is designed to be installed in the protected environment within the tubular axle used on many relatively large vehicles, such as semi-trailers. A tone wheel is rotated by a drive connected to the vehicle hub cap which, of course, rotates with the vehicle wheel.